1. Field of the Invention
The present invention relates to an exhaust system. More particularly, the present invention relates to an exhaust system for reducing nitrogen oxide that is included in exhaust gas.
2. Description of Related Art
Generally, exhaust gas that is exhausted through an exhaust manifold of an engine is induced to pass through a catalytic converter that is mounted in the middle of an exhaust pipe to be purified, and the noise thereof is reduced while passing through a muffler before the exhaust gas is discharged to the outside through a tail pipe.
The catalytic converter processes the pollution materials that are included in the exhaust gas. Further, a particulate filter is mounted on the exhaust pipe to trap particulate material (PM) that is included in the exhaust gas.
A selective catalytic reduction device is a type of catalytic converter. Reducing agents such as carbon monoxide, total hydrocarbon (THC), and so on react well with nitrogen oxide rather than oxygen in the selective catalyst reduction apparatus (SCR), which is why it is called a selective catalyst reduction apparatus (SCR).
In an internal combustion engine to which the selective catalyst reduction apparatus is installed, the fuel is continuously and additionally injected additionally according to the nitrogen oxide amount in the exhaust gas. Accordingly, the hydrocarbon can be slipped from the selective catalyst reduction apparatus, and the fuel consumption is increased.
Also, when the reducing agent is continuously supplied, an oxidation/reduction reaction is also continuously performed in the exhaust pipe. Accordingly, the durability of the catalyst is deteriorated by reaction heat that is formed during the oxidation/reduction reaction.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.